1. Field of the Invention
This invention relates to an improved pneumatically actuated proportioning pump and more specifically to a pump to be used in the petroleum industry in a dehydrator system for natural gas.
There are a variety of pneumatically actuated pumps that are either single acting or double acting, with the capacity to pump a variety of fluids and semi-fluids. In such pumps there is incorporated a reciprocating drive piston in a chamber that is connected axially to a pumping piston in a different chamber. The reciprocation of the drive piston and the pumping piston is controlled by a control valve that is actuated by the positon of the drive piston or the pumping piston. The driving and pumping chambers can be attached in a common main body, or can be separate chambers that are mechanically connected by a piston connecting rod.
Pumps of this type having positive displacement cylinders with reciprocating pistons are for the most part driven by a pressurized gaseous medium that is either exhausted to the atmosphere or to a waste sink. In particular, the proportioning pump that is used in a dehydrator system uses natural gas as the driving medium and the natural gas is exhausted to the atmosphere. The natural gas which is exhausted to the atmosphere by present proportioning pumps cannot be economically recovered and is thus wasted by the dehydrator system.
In the current technology of the proportioning pumps, the discharge pressure of the displacement medium in the drive cylinder must be at atmosphere pressure. Superatmospheric pressure conditions on the discharge causes the pump to stall or to become less efficient in a direct ratio to the increase in the back pressure on the discharge.
The pumps which are gas pressure actuated, either single or double acting, usually are provided with interconnecting reciprocating actuating and pumping pistons both being accommodated in their own chambers and with the actuating or driving piston having a larger cross-sectional area than the pumping piston. The mechanism of pumping with this configuration only can be accomplishd by a valving system that allows the medium being pumped to enter into the pumping chamber during a suction stroke of the pumping piston. The suction stroke of the pump can be accomplished either by means of the plurality of actuating and pumping pistons or by means of a helical spring that returns the actuating piston to the normally stable position. The valving system that is open on the suction stroke is normally closed on the pumping stroke. The discharge ports of these pumps have valving systems that operate opposite to the suction valve. The valve on the discharge port is normally closed during the suction stroke of the pumping piston and is opened by the medium being pumped during the pumping stroke of the piston.
The above described valving system is an integral part of the pump and must be fixed securely to the pump by a threaded or clamping device. This assembly of valve has a disadvantage that the pump discharge or suction must be disassembled in order to maintain a malfunctioning valve. A further disadvantage is to be seen in the fact that the valving mechanism must be designed and manufactured specifically for each pump configuration.
The prior construction of a high pressure pneumatically actuated reciprocating proportioning pump required careful design sealing rings or glands between the drive chamber and the pumping chamber. The sealing mechanism only could be manufactured with careful precision on special machines.
2. Description of Related Art
Various different forms of proportioning and other pumps including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 2,858,162, 3,201,031, 3,825,122, 4,104,008, 4,119,113, 4,390,322 and Re.25,873.
However, these previously known forms of proportioning and other similarly constructed pumps usually require excessive pump disassembly in order to repair or replace a valve and further require excessive precision machining and sealing.